The present invention relates to flywheels, particularly to concentric, multi-ring rotors or flywheels, and more particularly to an expandable separator/torque coupler intermediate adjacent concentric rings of a rotor, such as a flywheel.
The use of flywheels for the storage of energy has long been known, and the application of flywheels for vehicular use was initiated decades ago. The storage of energy in a flywheel to power an electric vehicle was utilized, for example, over forty years ago to operate an electric-drive bus, known as the Gyrobus. In this electric-drive bus, occasional charging stops were required for an electric motor to spin up a heavy steel flywheel, and in motion this flywheel provided energy to power the motor connected to it, which then operated as a generator, to provide electricity to drive other electric motors that turned the wheels of the bus. Using the reversibility of the generator-motor, in slowing down or on downhill runs the bus spun up the flywheel, thus providing a "regenerative" braking action that at the same time recovered some of the energy expended in traction. The main drawbacks were the cumbersome steel flywheel and the cumbersome and expensive power conversion equipment.
The use of flywheels in the form of an electromechanical battery (EMB) was extensively researched in the 1970-1980 time period for use in electric vehicles. It was determined from these efforts that the addition of one or two EMB's to their conventional battery system could greatly improve the performance of the electric vehicles.
With the development of strong, lightweight materials and solidstate electronics, EMB's were again considered for electric vehicle use, as well as for large stationary application. Such materials included fiber composites, with the flywheels which included contrarotating rotors each being composed of multiple, concentric rings. For example, compact cylindrical flywheels using unidirectionally wound flexible fibers were developed, and U.S. Pat. Nos. 3,683,216 issued Aug. 8, 1972 to R. F. Post, and No. 3,741,034 issued Jun. 26, 1973 to S. F. Post exemplify flywheels with multi-ring, contrarotating rotors.
Further research and development efforts have been directed to fiber composite flywheels using a multi-ring design. For example, one approach consisted of separate thin-walled cylinders or rings fabricated of filament-wound unidirectional fibers embedded in an epoxy matrix, and the cylinders were coupled together by elastic elements or spring-like mechanical elements that transmit torques but did not transmit strong radial forces. Such an approach, along with an extensive history of flywheel development is set forth in a paper UCRL-JC-110861, "A High Efficiency Electromechanical Battery", R. F. Post et al., Jun. 11, 1992.
Concentric ring or multi-ring flywheels have unique features that minimize radial tensile stress allowing higher speeds and increased stored energy. However, a difficult aspect of this methodology is that the concentric rings expand differentially with different radius rings. This differential expansion between rings requires expandable separators to take up the gap between adjacent rings. These separators are required to be dynamic components. While elastic and spring-like elements were utilized to interconnect the cylinders or rings of the flywheel described in the above-referenced paper UCRL-JC-110861, such did not effectively provide for the differential expansion of the various rings, or maintain a torque and centering attachment between the adjacent rings. Thus, a need exists for a simple, yet effective means to resolve the problem associated with differential expansion of the various rings in a concentric rotor or flywheel.
The present invention provides a solution to this problem by utilizing an expandable separator/torque coupler between adjacent rings of a concentric ring rotor or flywheel. This is accomplished by an expandable hook ring carbon fiber separator/torque coupler, wherein a hook ring section thereof is positioned over an upper end of an inner ring of a multi-ring arrangement, and wherein a flanged section thereof is positioned under and adjacent outer ring, such that the expandable separator/torque coupler maintains a torque and centering attachment between the adjacent concentric rings, thereby reducing the adverse effects resulting from differential expansion of different radius concentric rings.